text: In popular culture, hand boilers used to be sometimes known as "love meters" because the tube that separates the upper and lower bulbs is twisted into a heart shape and the volatile liquid is colored red. Love meters were a common collectors item or a souvenir. Depending on how the item was packaged, one would grasp the lower bulb to "prove" how passionate one was, or a couple would each grasp one end to see who would force the liquid into the others bulb.
  Hand boilers are much more commonly used as a scientific novelty today.